This application relates generally to inspecting objects, and more specifically to methods and apparatus for inspecting objects using a light measurement system.
Objects are sometimes inspected, for example, to determine a size and/or shape of all or a portion of the object and/or to detect defects in the object. For example, some gas turbine engine components, such as turbine or compressor blades, are inspected to detect fatigue cracks that may be caused by vibratory, mechanical, and/or thermal stresses induced to the engine. Moreover, and for example, some gas turbine engine blades are inspected for deformations such as platform orientation, contour cross-section, bow and twist along a stacking axis, thickness, and/or chord length at given cross-sections. Over time, continued operation of the object with one or more defects may reduce performance of the object and/or lead to object failures, for example, as cracks propagate through the object. Accordingly, detecting defects of the object as early as possible may facilitate increasing the performance of the object and/or reducing object failures.
To facilitate inspecting objects, at least some objects are inspected using a light measurement system that projects a structured light pattern onto a surface of the object. The light measurement system images the structured light pattern reflected from the surface of the object and then analyzes the deformation of the reflected light pattern to calculate the surface features of the object. However, because many manufactured objects have a wide range of shapes and reflectivities, data obtained from some known light measurement systems may be less optimal than desired because of variables such as the angle of view of the light source, uneven reflections from the object, and/or noise caused by ambient light and/or multiple bounce reflections of the emitted light. Accordingly, such variables may result in reduced image quality and poor measurement results, possibly leading to an incorrect interpretation of surface features of the object.
Some known light measurement systems optimize the angle of view of the light source by taking a series of data sets and guessing at the best position of the light source based on the data sets. However, this may be difficult and/or time consuming. Moreover, at least some known light measurement systems include a physical mask that is formed, for example, from a sheet of paper or metal. The physical mask limits an area illuminated by the light source to facilitate reducing inter-reflections between the test fixture and the object. However, such physical masks are sometimes formed by electronically tracing an outline of the object as seen from the light source, which may be time consuming and/or difficult. Refinement of such masks is sometimes only done visually, which may further increase a time and/or difficulty of fabricating such a physical mask.